The shift to stage 6 caught some of South Africa's biggest cities flat-footed, with both Ekurhuleni and Johannesburg telling customers they had no schedules for such an eventuality, and could not say which parts of the cities would be blacked out when.

At every stage of load shedding, Eskom rations the country by a further 1,000MW of power, the equivalent of 1,000,000 kilowatts (A microwave or kettle uses around 1 kilowatt, so one way to think of the stages is that at every escalation, Eskom switches off a million kettles.)

At stage 1, South Africa as a whole is forced to save 1,000MW, or a million kettles, which – depending on the choices of local governments – mean either short outages for individual electricity users or blackouts in only small parts of cities.

At stage 2 the national grid is short 2,000MW, or two million kettles, at stage 3 rationing reaches 3,000MW, and so on.

How suburbs and towns are affected by every stage depends on a range of factors, including what time of day the electricity emergency is declared. The exact social and economic impact is hard to estimate, and guesses range widely .